Solved UPSC CDS/OTA Question
A solved UPSC CDS/OTA PYQ — decoded step-by-step.
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Q · Time and WorkMedium · 45s
Pipe A fills a tank in 10 hours, Pipe B in 15 hours. Both are opened for 4 hours, then Pipe A is closed. How much time will Pipe B take to fill the remaining part?
TopicTime and Work
Question Typemultiple choice
DifficultyMedium
Marking+1 / −0.25
Test Duration30 min
Step-by-Step Solution
The complete worked solution.
Every step explained — no skipped algebra.
In 4 hours, they fill 4×(1/10+1/15)=4×(1/6)=2/3 tank. Remaining = 1/3, Pipe B fills at 1/15/hr → 5 hours for whole tank, so 1/3 takes 5/3 = 1h 40m.
Final Answer: Option A — 3 hours